Microfluidic apparatuses

According to an example, a microfluidic apparatus may include a fluid slot, a foyer in fluid communication with the fluid slot via a channel having a relatively smaller width than the foyer, a sensor to detect a presence of a particle of interest in a fluid passing through the channel, a nozzle in fluid communication with the foyer, and an actuator positioned in line with the nozzle. The microfluidic apparatus may also include a controller to receive information from the sensor, determine, from the received information, whether a particle of interest has passed through the channel, and control the actuator to expel fluid in the foyer through the nozzle based upon the determination.